Secondary recovery of petroleum oil by desulfovibrio



Patented Nov. .24, 1953 UNITED STATES PATENT OFFICE SECONDARY RECOWJRYOF PETROLEUM OEL BY DESULFOVIBRIO No Drawing. Application August 27,1949,

' Serial No. 112,836

4 Claims. 1

This invention relates to recovery of petroleum oil from oil-bearingearth formations and relates more particularly to secondary recovery ofpetroleum oil from these formations.

Petroleum oil is generally recovered from oilbearing earth formationsinitially as a result of gas pressure, rock pressure, or natural waterdrive forcing the oil from the formation through the poducing well tothe surface. As oil production continues, the reservoir energy graduallydecreases and finally becomes insumcient to iorce the oil to thesurface, although a major portion of the original quantity of the oil inthe formation still remains therein. To increase the ultimate recoveryof the oil, pumping is then employed but when the rate of recovery bypumping falls to an uneconomically low level, a further increase in theultimate recovery of the oil may still be economically effected by theemployment of secondary recovery methods such as gas drive or waterflooding.

It has recently been proposed to facilitate or increase the recovery ofpetroleum oil from an oil bearing earth formation by subjecting theformation to the action of oil-releasing bacteria. Apparently, thefacilitation or increase in the recovery of petroleum oil by thesebacteria, which are sulfate reducers, is the result of a number offactors such as production of acids which dissolve the formation andincrease its porosity, production of carbon dioxide which increases gaspressure in the formation, production of detergents or surface-activesubstances which effect release of adsorbed oil and reduce surfacetension, and conversion of high molecular weight hydrocarbons to lowermolecular weight hydrocarbons with consequent reduction in viscosity ofthe oil. The oil-releasing, sulfate-reducing bacteria are able toutilize as nutrients, or sources of energy, the petroleum hydrocarbonshaving a molecular weight greater than decane present in oil-bearingearth formations, and thereby are able to remain active and to multiplywithin oilbearing formations. However, petroleum oil as a source ofenergy for oil-releasing bacteria provides for only slow and limitedmultiplication and low activity, with the result that release of oilfrom the oil-bearing formation is slow and incomplete.

It is an object of this invention to provide a method for secondaryrecovery of petroleum oil from oil-bearing earth formations. It isanother object of this invention to increase the rate and extent ofrecovery of petroleum voil from oilbearing earth formations subject tothe action of oil-releasing bacteria. It is another object of thisinvention to increase the multiplication and activity of oilereleasingbacteria in an oilbcaring earth formation. It is another object of thisinvention to increase the extent of recovery of petroleum oil from anoil-bearing earth formation by water flooding. These and other objectsof the invention will become apparent from the following descriptionthereof.

In accordance with our invention, secondary recovery of petroleum oilfrom an oil-bearing formation subject to the action of oil-releasingbacteria is effected by driving therethrough water containing a nutrientcomprising molasses for the oil-releasing bacteria.

The oil-releasing bacteria known to facilitate and increase the recoveryof petroleum oil from an oil-bearing earth formation are thehydrocarbon-oxidizing species of the genus Desu-lfo- Vibrio, namely,Desulfovibrio hydrocarbonoclasticus and Desulfouibm'ohalohydrocarbonoclasticus. The Desulfom'brio halohydrocarbcnoclasticusspecies distinguish from the Des-ulfouihrio hydrocarbonoclasticusspecies in their ability to be active and to multiply in the presence ofsalt water of high concentration, for example, solutions containing ashigh as 300,090 parts per million of salt. Both species are anaerobicand require water for their multiplication and activity. In addition towater, they require a number of dissolved mineral elements includingphosphorus (as phosphate ion) sulfur (as sulfate ion), nitrogen (asammonium or nitrate ion) and iodine, potassium, calcium, and ferrousiron ions. Carbon is also required and they may utilize carbon dioxideor organic matter, such as petroleum oil, as the source of carbon. Thesebacteria are active and multiply in an aqueous medium but the pH of themedium must be above 5.5 and not greater than 9.0, with an optimum pHbetween 6.0 and 8.5, and the temperature must not exceed about 180 F.

The hydrocarbon-oxidizing bacteria species of the genus Desulfov-ibrioare obtainable from many natural sources. They are found in marinesediments and in oil well waters. Desulfovibriohalohydrocarbonoclast'icus has been isolated from oil well brines andmarine muds and Desulfovibrio hydrocarbonoclasticus has been isolatedfrom muds obtained from the bottoms of fresh water lakes and rivers. Wehave found that Desalinoz'brio haZohg drocarbonoclasticus and Decalooibrio hydrocarbonoclasticus are present in many oil-bearing earthformations although they are not active in every formation in which theyare present most likely because of lack of nutrients or the presence ofinhibitory substances such as high concentrations of hydrogen sulfide.

In recovering petroleum oil from an oil-bearing earth formation by waterflooding, either fresh l;

or saline water is injected under pressure into one or more input wellsleading to the earth formation. The water migrates through theformation, forcing the oil contained in the formation before it andalong with it, to an output well or wells leading from the formation.The oil is then recovered from the output, or production, wells.

In the practice of our invention, a nutrient comprising molasses isadmixed with the water injected into the input well in quantitiessufficient to provide for the growth, multiplication, and activity oroil-releasing bacteria whereby the effectiveness of the water drive inrecovering petroleum oil from the oil-bearing formation is enhanced bythe bacterial activity. Where the oil-bearing formation does not containoil-releasing bacteria, a culture of hydrocarbon-oxidizing bacteria ofthe genus Desulfovibrio is admixed with the water containing themolasses. On the other hand, where the formation contains theoil-releasing bacteria, whether or not in active state, inoculation ofthe formation with the oil-releasing bacteria by admixture of a culturethereof with the injection water may not be necessary.

By molasses, we mean the uncrystallizable syrup obtained during boilingdown of raw cane sugar or raw beet sugar. The commercial product maycontain between about 50 and 75% by weight of carbohydrates and thecommerical product may be used in the practice of our invention. The useof molasses as a nutrient for oil-releasing bacteria is particularlyadvantageous in that molasses, in addition to containing carbohydrate inlarge quantities assimilable by bacteria, also contains proteinaceousnutrients as Well as growth factors, or vitamins, and mineralconstituents which are stimulating to the growth and multiplication ofbacteria. In this connection, molasses is commercially available inseveral grades, the grades differing from each other with respect totheir degree of refinement. The cruder grades of molasses, having beensubjected to a lesser degree of refinement, contain larger quantities ofgrowth factors and mineral constituents and, therefore, are preferred tothe more highly refined grades of molasses.

The molasses may be added to the injection water in various quantities.We have found that the addition of about 100 to 2,000 parts of molassesto one million parts of water effects more rapid multiplication and morerapid and complete release of petroleum oil from oil-bearing earthmaterials than can be achieved in the absence of such added nutrient.However, larger or smaller amounts of molasses may be added to theinjection water as desired particularly in view of the fact that thecarbohydrate concentration of the molasses may vary. Preferably, thequantity of molasses employed should be equivalent to at least 50 partsof carbohydrate to one million parts of injection water. Quantities ofmolasses may be employed equivalent to more than 1,000 parts ofcarbohydrate per million parts of injection water, but ordinarily thereis no particular advantage in using these larger quantities. Themolasses may be added continuously to the injection water so that theinjection water as it enters the input well will con tain the desiredconcentration of molasses. However, the molasses may be addedintermittently to the injection water, as, for example, once every houror other suitable time interval, the amount being added intermittentlybeing sufficient, of course, to obtain, on the average, the desiredconcentration with respect to the amount of water injected into thewell.

As previously mentioned, Desulfooibrio halohydrocarbonoclasticus andDesuljooibn'o hydrocarbonoclastz'cus require, in addition to a nutrient,various mineral elements. Many of these elements are found in naturalwater sources or in oil-bearing earth formations and, accordingly, freshwater or salt water obtained from natural sources and employed in waterflooding will supply the mineral elements required for growth,multiplication, and activity of these bacteria, or the elements will besupplied when the water reaches the oil-bearing formation. However,where neither the water supply nor the formation will supply thenecessary mineral elements, they may be admixed with the injection wateras part of the nutrient. Additionally, as previously stated,Desulfovibrio halohydrocarbonoclasticus and Desulfooibr'iohydrocarbonoclasticus require an equeous medium having a pH above 5.5and not greater than 9.0. The pH of natural waters will generally beabout 7.5 and are therefore satisfactory as a medium for these bacteria.Further, most oil-bearing earth formations contain calcium carbonatewhich will maintain water injected into the formation at a proper pH forbacterial growth and activity. However, the oil-releasing bacteria,through reduction of sulfate and assimilation of the molasses, mayproduce acids reducing the pH of the aqueous medium to a point wheregrowth and activity of the bacteria are inhibited. It is accordinglynecessary, where the formation does not contain calcium carbonate orother alkaline material in sufficient quantity to react with theproduced acids and maintain the injection water at proper pH, to add abuffer or buffers, such as phosphates or carbonates, to the injectionwater in addition to the molasses and in addition to the other mineralelements, if addition of other mineral elements is necessary. Theinjection water, after injection into the formation, should preferablycontain the following, as mineral elements required by the bacteria:

5. Where the oil releasing bacteria are Desulfovibriohalohydrocarbonoclasticus, the injection water, after injection into theformation, should contain, in addition to the above, sodium chloride ina concentration at least as high as 20,000 parts per million.

The desired mineral elements and buffers may be added to the injectionwater prior to injection into the oil-bearing earth formation. However,as previously stated, natural waters contain many or all of thesemineral elements and where natural waters are employed, they may firstbe analyzed to determine the kind and concentration of mineral elementscontained therein and, thereafter, the mineral elements in which theyare deficient for bacterial growth and activity, as determined by theanalysis, added thereto. Further, from knowledge of the chemicalcomposition of the oil-bearing earth formation, it can be determinedwhether the injection water, after injection into the formation, willdissolve from the formation any of the mineral elements or bufiersdesired, and these mineral elements and buffers need not be added to thewater prior to injection.

If mineral elements and buifers are added to the injection water, theymay be added in admixture with the molasses or added separately.Further, they may be added continuously or intermittently to theinjection water, and, where added intermittently, the amount, of course,must be suiiicient to obtain, on the average, the desired concentrationwith respect to the amount of water injected into the formation.

[is mentioned hereinbefore, where the oilbearing earth formation doesnot contain Desalfooibrio haZohg/drocarbonoclasticus or Desulfovibrz'olig/drocarbonoclasticus, a culture of either of these bacteria isadmixed with the injection water. Cultures of these bacteria may beprepared in various ways. As an example, a culture of Desulfovibriohydrocarbonoclasticus may be prepared by adding a bacterial sourcematerial such as water from a subterranean earth formation or a mud fromthe bottom of a fresh water lake or river to a sterile aqueous solutioncontaining the following:

Parts per million Magnesium sulfate 500 Sodium carbonate 100Monopotassium phosphate 100 Ammonium sulfate 1,000 Ferrous sulfate(FeSOMI-IzO) 50 Molasses 500 and incubating for a suitable period oftime which may be between three and nine days. The temperature ofincubation may be between 70 F. and 180 F., and should be the sametemperature as the temperature of the oil-bearing earth formation to betreated, in order to obtain bacteria acclimatized to the formationtemperature. The culture thus obtained, termed an enrichment culture, isadmixed with the injection water. An enrichment culture of Desuljovibriohalohydrocarbonoclasticus is prepared, for example, by adding abacterial source material obtained from an oil well brine or a saltwater marine mud to a sterile aqueous solution similar to the solutionpreviously mentioned but containing 20,000 parts per million of sodiumchloride, and incubating for a suitable period of time preferably at thetemperature of the earth formation to be treated.

We have discovered that, while molasses provides a suitable nutrient forDesuljom'brio halohydrocarbonoclasticus and Desulfovibriohydrocarbonoclasticus, these bacteria utilize the molassee more readilyin the presence of a symbiont. By symbiont, we mean a dissimilar speciesof bacteria living in intimate association with the desiredoil-releasing bacteria, and the association is advantageous to both ofthe bacteria. Enrichment cultures prepared through the use of naturalbacterial source materials such as formation waters or salt or freshwater muds will contain symbionts for the oil-releasing bacteria.Further, the oil-releasing bacteria in oil-bearing earth formations willcontain symbionts. However, where pure cultures of Desulfovibrz'ohalohydrocarbonoclasticus or Desulfovibrio hydrocarbonoclasticus areemployed, symbionts may be provided by admixing with the pure culture, aculture of bacteria obtained from a natural source such as naturalformation water, marine mud, or ordinary garden soil,

The following example will be illustrative of the results to be obtainedby our invention:

A petroleum oil-bearing sand from which the oil was not flowing bynatural means was subjected to water flooding until no further removalof oil could be effected. Approximately 50% of the oil originallycontained in the sand was removed by this procedure. The sand was thenflooded with a natural water containing a culture of DesulfovibriohaZohydrocarbonoclasticus and 100 parts per million by weight ofmolasses. The mineral content of the water in parts per million was asfollows: phosphate-70, ammonium-270, sulphatel,147, iodide3,magnesium100, potassium-29, ferrous ir0nl0, calmum-75, and sodiumcarbonate-100. By this second procedure, approximately 35% of the oilremaining in the sand was removed.

By the procedure of our invention, a greatly increased recovery ofpetroleum oil from an oilbearing sand can be effected. Further,oil-bearing earth formations from which oil can no longer be recoveredby water drive can be treated by the procedure of our invention toeffect a substantial recovery of the remaining oil.

Having thus described our invention, it is to be understood that suchdescription has been given by way of illustration and example only andnot by way of limitation, reference for the latter purpose being had tothe appended claims.

We claim:

1. In the method for the recovery of petroleum oil from an oil-bearingearth formation by the injection of water through an input well to saidformation, the improvement comprising admixing with said water prior toinjection to said formation a culture of bacteria of thehydrocarhon-oxidizing species of the genus Desulfovibrio and a nutrientfor said bacteria comprising molasses.

2. In the method for the recovery of petroleum oil from an oil-bearingearth formation by the injection of water through an input well to saidformation, the improvement comprising admixing with said water prior toinjection to said formation a culture of bacteria of the speciesDesulfovibrio halohydrocarbonoclasticus and a nutrient for said bacteriacomprising molasses.

3. In the method for the recovery of petroleum oil from an oil-bearingearth formation by the injection of water through an input well to saidformation, the improvement comprising admixing with said water prior toinjection to said formation a culture of bacteria of the speciesDesulfom'brio hydrocarbonocldsticus and a 7 nutrient for said bacteriacomprising molasses. 4. In the method for the recovery of petroleum oilfrom an oil-bearing earth formation by the injection of water through aninput well to said formation, the improvement comprising admixing withsaid water prior to injection to said formation a culture of bacteria ofthe hydrocarbon oxidizing species of the genus Desulfovibrio a cultureof a symbiont bacteria, and a nutrient for said bacteria comprisingmolasses.

DAVID M. UPDEGRAFF.

GLORIA B. WHEN.

8 References Cited in the file of this patent UNITED STATES PATENTS2,485,385 OTHER REFERENCES Zobell, Bacterial Release of Oil, World Oil,August 25, 1947, pages 36, 39-40, 42, 44, 47.

1. IN THE METHOD FOR THE RECOVERY OF PETROLEUM OIL FROM AN OIL-BEARINGEARTH FORMATION BY THE INJECTION OF WATER THROUGH AN INPUT WELL TO SAIDFORMATION, THE IMPROVEMENT COMPRISING ADMIXING WITH SAID WATER PRIOR TOINJECTION TO SAID FORMATION A CULTURE OF BACTERIA OF THEHYDROCARBON-OXIDIZING SPECIES OF THE GENUS DESULFOVIBRIO AND A NUTRIENTFOR SAID BACTERIA COMPRISING MOLASSES.